Federal Bureau of Investigation agents have finally ditched paper files for a new computer system, an effort that took 12 years and cost more than $600 million.

The system, called Sentinel, includes elements resembling Web browsers, with tabs and movable windows, and forms that are filled out in a question-and-answer format similar to consumer tax software.

An FBI special agent demonstrated the system, which went live July 1, to reporters Tuesday. Agents can share files electronically and can track changes made by others. RSS feeds, commonly used in Web browsers to aggregate news topics, can be used to track updates on files.

Agents can also use a search feature, entering a phone number, for instance, to see if it occurs in other active cases or leads.

One of the biggest hurdles to getting agents to accept the system, Mr. Johnson said, has been their reluctance to believe it’s really happening.